The Fourth National Institutes of Health Symposium on the Functional Genomics of Critical Injury: Surviving stress from organ systems to molecules

Altered serum stress neuropeptide levels in critically ill individuals and associations with lymphocyte populations

OBJECTIVE

Potential physiological correlates of stress and the role of stress neuropeptides, other than those of the hypothalamic-pituitary-adrenal axis, in critical illness have not been addressed. We investigated: (a) serum levels of stress neuropeptides (ACTH, substance P (SP), neuropeptide Y (NPY), cortisol, prolactin) in critically ill individuals compared to matched controls, (b) associations with lymphocyte counts, (c) associations among stress neuropeptide levels, and (d) associations with perceived intensity of stress, critical illness severity and survival.

METHODS

Correlational design with repeated measures. Thirty-six critically ill patients were followed up for 14 days compared to 36 healthy matched controls. Stress was assessed by the ICUESS scale. Correlations, cross-sectional comparisons and multiple regression models were pursued.

RESULTS

For the first time, we report lower SP (Difference of means (DM) = 2928-3286 ng/ml, p < 0.001) and NPY (DM = 0.77-0.83 ng/ml, p < 0.0001) levels in critically ill individuals compared to controls. Cortisol levels were higher (DM = 140-173 ng/ml, p<0.0001) and lymphocyte population counts (p < 0.002) were lower in patients throughout the study. NPY levels associated with lymphocyte (r = 0.411-0.664, p < 0.04), T-lymphocyte (r = 0.403-0.781, p< 0.05), T-helper (r = 0.492-0.690, p < 0.03) and T-cytotoxic cell populations (r = 0.39-0.740, p < 0.03). On day 1, cortisol levels exhibited associations with lymphocyte (r = -0.452, p = 0.01), T-cell (r = -0.446, p = 0.02), T-helper (r = -0.428, p = 0.026) and T-cytotoxic cells ( r = -0.426, p = 0.027). ACTH levels associated with NK cell counts (r = 0.326-0.441, p < 0.05). Associations among stress neuropeptides levels were observed throughout (p < 0.05). ACTH levels associated with disease severity (r = 0.340-0.387, p < 0.005). A trend for an association between ACTH levels and intensity of stress was noted (r = 0.340, p = 0.057).

CONCLUSION

The significantly lowered NPY and SP levels and the associations with cortisol, ACTH and lymphocytes suggest that the role of these peptides in critical illness merit further investigation. Future studies need to address associations between these neuropeptides and functional immune cell responses and inflammatory markers in critical illness.

Interpersonal touch: physiological effects in critical care

INTRODUCTION

Nurses use several forms of touch in patient encounters. Interpersonal touch elicits specific physiological and psychological responses, including neuroendocrine effects and reduction of stress. Critical illness is a state of excessive physiological and psychological stress.

AIMS

To critically review evidence on the effect of touch on physiological outcomes in critically ill individuals. Results of intervention studies in adult critical care settings were reviewed along with supportive evidence from studies in other populations.

METHODS

Critical literature review based on studies published in MEDLINE, PubMed, Cinahl, Embase, and Cochrane databases.

RESULTS

Eleven studies were reviewed. Significant effects of interpersonal touch included lower systolic and diastolic blood pressure and respiratory rate, improved sleep, and decreased pain. Almost no results were replicated owing to discrepancies among studies. Although the effect of touch on cardiovascular autonomic status appears considerable, several confounders must be considered. In noncritically ill populations, replicable findings included increased urinary dopamine and serotonin, natural killer cytotoxic activity, and salivary chromogranin. Effects on plasma cortisol and immune cells were variable. Effects appear to vary according to amount of pressure, body site, duration, and timing: Moderate pressure touch may elicit a parasympathetic response in contrast to light touch, which may elicit a sympathetic response. Moreover, touch effects may be mediated by the density of autonomic innervation received by the body areas involved and repetition of sessions.

CONCLUSION

The physiological pathway mediating the effects of touch is unclear. Although no concrete conclusions can be drawn, research evidence suggests that touch interventions may benefit critically ill individuals.

Toward computational identification of multiscale "tipping points" in acute inflammation and multiple organ failure

Sepsis accounts annually for nearly 10% of total U.S. deaths, costing nearly $17 billion/year. Sepsis is a manifestation of disordered systemic inflammation. Properly regulated inflammation allows for timely recognition and effective reaction to injury or infection, but inadequate or overly robust inflammation can lead to Multiple Organ Dysfunction Syndrome (MODS). There is an incongruity between the systemic nature of disordered inflammation (as the target of inflammation-modulating therapies), and the regional manifestation of organ-specific failure (as the subject of organ support), that presents a therapeutic dilemma: systemic interventions can interfere with an individual organ system's appropriate response, yet organ-specific interventions may not help the overall system reorient itself. Based on a decade of systems and computational approaches to deciphering acute inflammation, along with translationally-motivated experimental studies in both small and large animals, we propose that MODS evolves due to the feed-forward cycle of inflammation → damage → inflammation. We hypothesize that inflammation proceeds at a given, "nested" level or scale until positive feedback exceeds a "tipping point." Below this tipping point, inflammation is contained and manageable; when this threshold is crossed, inflammation becomes disordered, and dysfunction propagates to a higher biological scale (e.g., progressing from cellular, to tissue/organ, to multiple organs, to the organism). Finally, we suggest that a combination of computational biology approaches involving data-driven and mechanistic mathematical modeling, in close association with studies in clinically relevant paradigms of sepsis/MODS, are necessary in order to define scale-specific "tipping points" and to suggest novel therapies for sepsis.

Systems biology in critical-care nursing

Systems biology applies advances in technology and new fields of study including genomics, transcriptomics, proteomics, and metabolomics to the development of new treatments and approaches of care for the critically ill and injured patient. An understanding of systems biology enhances a nurse's ability to implement evidence-based practice and to educate patients and families on novel testing and therapies. Systems biology is an integrated and holistic view of humans in relationship with the environment. Biomarkers are used to measure the presence and severity of disease and are rapidly expanding in systems biology endeavors. A systems biology approach using predictive, preventive, and participatory involvement is being utilized in a plethora of conditions of critical illness and injury including sepsis, cancer, pulmonary disease, and traumatic injuries.

Toward an integrated research agenda for critical illness in aging

Aging brings an increased predisposition to critical illness. Patients older than 65 years of age account for approximately half of all intensive care unit (ICU) admissions in the United States, a proportion that is expected to increase considerably with the aging of the population. Emerging research suggests that elderly survivors of intensive care suffer significant long-term sequelae, including accelerated age-related functional decline. Existing evidence-based interventions are frequently underused and their efficacy untested in older subjects. Improving ICU outcomes in the elderly will require not only better methods for translating sound science into improved ICU practice but also an enhanced understanding of the underlying molecular, physiological, and pathophysiological interactions of critical illness with the aging process itself. Yet, significant barriers to research for critical illness in aging exist. We review the state of knowledge and identify gaps in knowledge, research opportunities, and barriers to research, with the goal of promoting an integrated research agenda for critical illness in aging.